Size Effects on Photodissociation and Caging of Hydrogen Bromide Inside or on the Surface of Large Inert Clusters:  From One to Three Icosahedral Argon Layers

Abstract

Molecular dynamics simulations have been employed for the study of photolysis of hydrogen bromide placed inside or on the surface of Ar 12 , Ar 54 , Ar 97 , and Ar 146 clusters, representing one to three icosahedral solvation shells. A large set of classical Wigner trajectories, which take into account the initial quantum rotational or librational delocalization of HBr, is generated and analyzed in terms of transient hydrogen populations inside the cluster and final kinetic energy distributions. The key result is that for fully solvated HBr the size effect on caging is dramatic in the studied range of cluster sizes, while it is only moderate for surface isomers. Simulations also demonstrate that caging can be efficiently turned off by a librational preexcitation of HBr on argon clusters. Calculations are compared to results of cluster experiments which have measured the kinetic energy distribution of hydrogens originating from HBr photolysis at 243 nm in or on argon clusters with an average size of 115 atoms, and a near-quantitative agreement is found.

One-Electron Pseudo-Potential Determination of Stable Isomers of the Li*Ar n Excited Clusters: Absorption Spectra

“…CaBr * ? H reaction has been photo induced starting from the Ca…Br complex that is deposited at the surface of a large argon cluster [30]. Clearly, such studies benefit of a good knowledge of the interaction between the reactants and the cluster environment.…”

Wave packet study of the UV photodissociation of the Ar2HBr complex

“…While most of the studies were devoted to the one-atom cage effect ͑Rg-HX͒ [1][2][3][4][5][6][7][8][9][10][11][12][13][19][20][21][26][27][28][29][30] or to the cage effect in or on large clusters where the first solvation shell is closed ͑Rg n with n ജ 12͒, [15][16][17]22,23,25,[31][32][33] relatively little attention has been paid to the cage effect in the Rg n -HX systems with 1 Ͻ n Ͻ 12, and the corresponding investigations concern uniquely the Ar n -HF and Ar n -HCl complexes. In particular, the capacity of an inert environment to hinder the photodissociation ͑and even cause, sometimes, recombination͒ of a solute molecule, also called cage effect, is a well-known and challenging topic.…”

Theoretical study of finite-temperature spectroscopy in van der Waals clusters. I. Probing phase changes in CaArn

“…4,5,6,7,8,9 Photodissociation of HBr on argon clusters has been investigated by Baumfalk et al, 4,5,6 including a theoretical study of the HBr-cluster interaction. 5 Chemiluminescence in the bimolecular reaction Ba+N 2 O−→BaO * +N 2 was the subject of a work by Gaveau et al, 7 and photodetachment in IHI − Ar n clusters was used to probe transition state spectroscopy of the I+HI reaction by Liu and coworkers. 8 One may also cite the photoinduced reaction dynamics between Ca * and HBr towards CaBr * +H at the surface of a large argon cluster carried out by Briant et al 9 Very recently, the reaction between N 2 O and Li 2 mediated by Ar n clusters has been investigated by Breckenridge and coworkers.…”